A swimmer in Boulder Creek at Eben G. Fine Park on May 8, 2022. Figuring out how much water is available to Boulder means navigating the complex world of Colorado water law and deducing how it pertains to the water rights held by Boulder. Credit: John Herrick

It flows from our faucets and shower-heads and flushes our toilets. But until water begins dripping from places it shouldn’t, few of us consider the liquid or the tangled piping carrying it around our homes. And what about before it enters our buildings? What’s water up to then? One possible deflection: If plumbing is such a mystery, how mountain snow becomes the stuff washing our clothes must be dismissed as far too complex for contemplation.

Kim Hutton, however, cannot enjoy the luxury of ignoring our water’s origin. As the water resources manager for the City of Boulder, assessing the amount of water the city needs and how much it has at its disposal is her livelihood. Where Boulder’s watershed protector (not her official title) Kate Dunlap focuses on water quality, Hutton deals with quantity.

And figuring out how much water is available to Boulder means navigating the complex world of Colorado water law and deducing how it pertains to the water rights held by Boulder.

“Some of [the city’s water rights] allow us to store water to be used later, so we can store it in our reservoirs,” Hutton said. “Other water rights can only be used immediately.”

In Colorado, water rights operate on a priority basis, to the jingle of: “First in time, first in right” (a notably less catchy version of “First come, first served”). Your place in line for getting water today relies on when you, or the irrigation ditch you’re utilizing, started using water initially — if your ditch started pulling from the creek in 1910, you’ll be ahead of the one that began in 1915, though behind the 1905 ditch, and so on. In Boulder’s climate, the earlier your ditch’s inception the better, because there’s not always enough water to go around.

“In 1888, the state developed a water law system,” Hutton said. “So everyone [using water] prior to 1888 had to come to court and say: ‘Here’s evidence I started using water in a certain year,’ and the state issued them a decree for whatever year [they could prove] they started using water.”

Irrigation ditches first established in Boulder still hold top water priority more than 150 years later. The most senior water right in town belongs to the Lower Boulder Ditch, whose decree dates back to 1859.

Owners of these high-priority irrigation ditches get to divert water to their crops or gravel pits before everyone else, no matter where they’re situated on Boulder Creek. Once they’ve received their water (and if there’s some left over) the person, or ditch, with the next highest priority receives theirs, and so on and so forth.

“The water user who’s furthest upstream might have to bypass a lot of water if their water right is not a priority to take it,” Hutton said. “So it’s not a geographically-based distribution of water; it’s a priority-based distribution.”

‘If it gets hotter and drier, we expect our demand to increase.’

When municipalities like Boulder began to settle and apply for water rights with the state, they received priorities well below those of the ditches that had been irrigating for years. One way to heighten your priority in the water world, however, is to purchase the rights of a higher-priority ditch and convert it from irrigation use to municipal use — which Boulder did.

“As the city was developing in the 1920s through the ‘60s, the city acquired quite a number of senior water rights,” Hutton said.

Despite purchasing several senior water rights, there are still ditches that have priority over the City of Boulder. This means some infrastructure owned by the city must be actively managed to ensure it is not encroaching on the rights of those downstream. 

Barker Reservoir near Nederland, for instance, is an “on channel” reservoir: The dam is located on the main river flow, versus an “off channel” reservoir where a diversion is required for water to reach the reservoir. Supplying Boulder with roughly one third of its water, Barker cannot begin filling until the rights of those downstream have been satisfied. Until that happens, Hutton and her team must monitor the flow rates of water entering Barker and try to match that with what they let storm out of the dam gates and rage into the canyon below.

This raises the question: What if those with senior priorities are wasting their water when there’s no water to waste? 

Colorado water law addresses this concern, stating that water used by decree cannot be wasted. Indeed, it must be put to one of many predetermined “beneficial” uses: from crop irrigation to “evaporation from a gravel pit.” The area’s water commissioner enforces this statute in addition to managing water priorities.

“When water use is really high, there’s a daily dialogue between water users and the water commissioner,” Hutton said. “The water commissioner is very conscientious to not allow a ditch or municipality to divert more than they need so they’re not wasting water. Water users make a request for water and the water commissioner will say yes, no, or how much.”

In the spring, when snow begins to melt and runoff begins, Boulder enters this fray of conversations with the water commissioner as it looks to fill its many reservoirs.

“The communication we have with the water commissioner is: Can we keep this water or do we have to let it pass through our reservoir?” Hutton said. “There are some cases, like this year, where we’re able to store a little bit of the water but not all of it. Some of that water is destined for downstream users who have a senior priority.”

Waiting for the city’s storage priorities to come into effect can produce hypertensive effects, because ensuring there’s water for a city that receives little rain requires a buffer. And some buffers for Boulder manifest as the previously mentioned Barker Reservoir, as well as several reservoirs in the Indian Peaks Wilderness: including Lakewood Reservoir and Silver Lake Reservoir.

“Storage in Colorado is both a drought reserve and, as we live in a semi-arid climate and there’s natural variability in water supply on an annual basis, it allows us to get through that natural variability,” Hutton said.

As climate change intensifies and results in a hotter, dryer Boulder, having reservoirs included in a broad portfolio of water rights is essential.

“As we look into the future, we’re looking at how climate change might affect the availability of our water supply and how it might affect demand,” Hutton said. “If it gets hotter and drier, we expect our demand to increase. 

“For the City of Boulder, we have a number of different water rights we could be using at any time. Part of our planning for resiliency is options. If option A isn’t available, is option B?”

Tim Drugan

Tim Drugan covers wildfires, water and other climate change-related issues for Boulder Reporting Lab with a focus on explanatory and solutions journalism. He also is the lead writer of BRL Today, our morning newsletter. Tim grew up in New Hampshire and graduated from UNH with a degree in English/Journalism.

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